I don't think you are in 'maintenance' mode yet. I still think you are fighting something in the water.

At 6pm Saturday night you had 13.8. Adding 2 jugs (I assume they are the 121-oz. and not gallons) would have added 9ppm which would put you at 22.8. Four hours later at 10pm, you had already lost 4.8. Then, you lost another 1ppm overnight. So, you actually lost 5.8 from sundown to sunup which is the time period we look at. (When you lose chlorine in the evening when there is no sun on the pool, it is lost due to oxidizing something in the water. When you lose it during the day, part of the loss is to the sun.)

It appears that your chlorine loss is lessening so hopefully you are getting close. I know you are getting frustrated but hang in there. I have a feeling that you are nearing the end. Report back in the morning.